1. Field of the Invention
The present invention pertains to an impact type device for delivering impact blow energy to internally threaded couplings for well pump rods and the like to release the threaded connection between the coupling and one or more rods.
2. Background
Oil well pump rods or so-called sucker rods, as well as certain percussion type drill rods, are interconnected end to end by generally cylindrical tubular threaded coupling members. In conducting repair or workover operations in an oil well, the elongated pump rod string or stem must be removed section by section so that certain repair work can be carried out. As each section of rod is raised to a position for removing the rod from the threaded coupling, a wrench is applied to each rod section to loosen the threaded connection between the external threads on the rod end and the internal threads in the coupling. These threaded connections are often very difficult to uncouple due to corrosion, over-tightening and thread deformation due to percussive forces. One technique for loosening the threaded connections between tubular couplings and pump rods is to deliver a series of impact blows to the external surface of the coupling member. This is somewhat difficult to accomplish since the coupling is a cylindrical member and the impact blows often, when delivered by a conventional hammer or the like, result in deflection of the hammer and inefficient transmission of energy, Occasionally, a coupling will fracture, resulting in pieces of the coupling striking objects or persons in the vicinity of the work. Still further, in oil well pump rods it is possible that some volatile fluid has leaked into the interior of the coupling which may aid in effecting bursting of the coupling member.
The above-mentioned problems with decoupling oil well pump rods and similar threadedly connected rods have been overcome with a device in accordance with the present invention wherein impact blows may be more effectively delivered to the coupling in the vicinity of the threaded connection between the coupling and the rod member and wherein a housing encircles or encloses the coupling to contain the coupling in the event of catastrophic failure thereof.